After you have finished sculpting your initial form, its time to create a wax copy of it that can be sprued and encased in ceramic shell. To do this you will first need to make a mold of your sculpture out of a material that can accept the application of the wax. Plaster works well for this, but synthetic materials like rubber and alginate work as well.

Note: It is not recommended that you use alginate as its usually only good for a couple of casts and quickly dries out/deteriorates and you may need to make multiple copies of your form in wax.

The above image is a WIP photo of the four part mold system i made for my wax casting. using synthetic materials is not neccessary but is more useful if you have a lot of undercuts and fine detail.

This is a completed image of my mold system that i made. its composed of two silicon rubber halves with a two part mother mold system made from plaster. 

Mold Making